This invention relates to pressure relief apparatus which is usable with food packing machinery to relieve packing compression when such machinery is stopped. While the mechanism of the present invention is applicable to machines designed for the packing of a wide variety of food products such as meats and vegetables, the mechanism is herein described in conjunction with a machine for packing tuna in so-called "chunk" or "flake" packs, an application with which this invention has been found to have particular utility.
To explain the environment and operation of a conventional tuna packing machine, reference is made to U.S. Pat. Nos. 4,330,252 and 3,346,403. The disclosures of such patents are incorporated herein by reference to illustrate conventional packing machine construction. In such machines, tuna in flake or chunk condition is fed into the machine and is directed into cylindrical cavities which continuously move through a path of travel. Pressure is applied to the product subsequent to the cavity-filling operation to fill voids, expel air, and to ensure a substantial and uniform pack of tuna in the cavities. After application of pressure, the resulting cake of tuna is trimmed to bring the amount which is to be canned to a predetermined weight. The compressed tuna cake is then transferred to a can or other container.
The pressure application process is critical because it determines the amount of tuna meat which will be packed into the predetermined volume. It also determines the moisture content of the resulting tuna cake. During automated operation of the tuna packing equipment, it may be necessary at certain times to stop the machinery while compression is taking place. Because the density of the tuna cake increases with time as compression is held constant, stopping the machine while it is in the compression mode will result in over-compression of the cake, which causes an excess amount of fluid to be compressed out of the tuna.
For these reasons, I determined it to be desirable to develop means for relieving compression when food product packing machinery must be stopped during production. It was therefore a general object of the present invention to develop such apparatus which is usable with conventional automated equipment designed to pack tuna and other meat and vegetable products. An additional object is that the apparatus should be simple in construction and therefore inexpensive to purchase, operate and maintain.